Graphene-PVA saturable absorber for generation of a wavelength-tunable passively Q-switched thulium-doped fiber laser in 2.0 μm

Graphene, a 2D material, has been used for generation of pulse lasers due to the presence of its various fascinating optical properties compared to other materials. Hence in this paper, we report the first demonstration of a thulium doped fiber laser with a wavelength-tunable, passive Q-switched output using a graphene-polyvinyl-alcohol composite film for operation in the 2.0 µm region. The proposed laser has a wavelength-tunable output spanning from 1932.0 nm to 1946.0 nm, giving a total tuning range of 14.0 nm. The generated pulse has a maximum repetition rate and average output power of 36.29 kHz and 0.394 mW at the maximum pump power of 130.87 mW, as well as a pulse width of 6.8 µs at this pump power. The generated pulses have a stable output, having a signal-to-noise ratio of 31.75 dB, and the laser output is stable when tested over a period of 60 min. The proposed laser would have multiple applications for operation near the 2.0 micron region, especially for bio-medical applications and range-finding

Gold cone metasurface MIC sensor with monolayer of graphene and multilayer of graphite

This report makes a comparison between the spectrum features of plasmonic metamaterial metal-insulator-conductor (MIC) sensor with a monolayer of graphene and another MIC sensor with a multilayer of graphite as the back reflector. In both structures, the silicon substrate as an insulator layer was sandwiched between sub wave length periodic nanogold cones as the first layer and graphene and graphite as the third layer, respectively. Nanolayer of chromium nano rods was also considered in the structure of MIC sensors as an interface layer between silicon and nanogold cone metasurface. The performance of the sensor was evaluated under different incident polarized light angles and different thickness of the metasurface when the metasurface infiltrated with seawater and air. The transmission spectrum of monolayer graphene-based MIC sensor, respecting to s-polarized waves, reveals prominent feature to detect the air rather than seawater in invisible regime. Meanwhile, the reflection spectrum of graphite-based MIC sensor provides ∼0 % reflection under resonance condition regarding s- and p-polarized waves for detecting air in visible spectrum

Hybridization of MMT/Lignocellulosic fiber reinforced polymer nanocomposites for structural applications: a review

In the recent past, significant research effort has been dedicated to examining the usage of nanomaterials hybridized with lignocellulosic fibers as reinforcement in the fabrication of polymer nanocomposites. The introduction of nanoparticles like montmorillonite (MMT) nanoclay was found to increase the strength, modulus of elasticity and stiffness of composites and provide thermal stability. The resulting composite materials has figured prominently in research and development efforts devoted to nanocomposites and are often used as strengthening agents, especially for structural applications. The distinct properties of MMT, namely its hydrophilicity, as well as high strength, high aspect ratio and high modulus, aids in the dispersion of this inorganic crystalline layer in water-soluble polymers. The ability of MMT nanoclay to intercalate into the interlayer space of monomers and polymers is used, followed by the exfoliation of filler particles into monolayers of nanoscale particles. The present review article intends to provide a general overview of the features of the structure, chemical composition, and properties of MMT nanoclay and lignocellulosic fibers. Some of the techniques used for obtaining polymer nanocomposites based on lignocellulosic fibers and MMT nanoclay are described: (i) conventional, (ii) intercalation, (iii) melt intercalation, and (iv) in situ polymerization methods. This review also comprehensively discusses the mechanical, thermal, and flame retardancy properties of MMT-based polymer nanocomposites. The valuable properties of MMT nanoclay and lignocellulose fibers allow us to expand the possibilities of using polymer nanocomposites in various advanced industrial applications

Fabrication, functionalization, and application of carbon nanotube-reinforced polymer composite: an overview

A novel class of carbon nanotube (CNT)-based nanomaterials has been surging since 1991 due to their noticeable mechanical and electrical properties, as well as their good electron transport properties. This is evidence that the development of CNT-reinforced polymer composites could contribute in expanding many areas of use, from energy-related devices to structural components. As a promising material with a wide range of applications, their poor solubility in aqueous and organic solvents has hindered the utilizations of CNTs. The current state of research in CNTs—both single-wall carbon nanotubes (SWCNT) and multiwalled carbon nanotube (MWCNT)-reinforced polymer composites—was reviewed in the context of the presently employed covalent and non-covalent functionalization. As such, this overview intends to provide a critical assessment of a surging class of composite materials and unveil the successful development associated with CNT-incorporated polymer composites. The mechanisms related to the mechanical, thermal, and electrical performance of CNT-reinforced polymer composites is also discussed. It is vital to understand how the addition of CNTs in a polymer composite alters the microstructure at the micro- and nano-scale, as well as how these modifications influence overall structural behavior, not only in its as fabricated form but also its functionalization techniques. The technological superiority gained with CNT addition to polymer composites may be advantageous, but scientific values are here to be critically explored for reliable, sustainable, and structural reliability in different industrial needs

Design and characterization of multiwavelength fiber laser in o-band transmission window / Siti Fatimah Norizan

This thesis presents the research work that has been carried out on O-band transmission windows as support to the saturated optical fiber transmission windows. O-band is selected based on advantages it offer including operational cost effectiveness, low absorption coefficient, low dispersion wavelength range and operated with existence system. The aim of this research work is to investigate the components that could be used in developing O-band as transmission windows. The components studied in this research work are the optical amplifiers and multiwavelength fiber laser as the transmitter. The optical amplifiers are Bismuth doped fiber amplifier (BiDFA), O-band Raman fiber amplifier (RFA) and Booster optical amplifier (BOA). The BiDFA produce low amplification (~2 dB) but high nonlinearity coefficient measured to be 13.98 W-1 km-1 utilizing the four wave mixing (FWM) effect. The RFA was tested with 4 different types of fiber, where dispersion compensated fiber (DCF) shows the highest amplification performance with gain of 12 dB for single pass configuration and 14 dB for double pass at 1330 nm signal wavelength. The BOA is an improved version of semiconductor optical amplifier (SOA) capable to amplify up to 28 dB and 31 dB at 1350 nm for single pass and double pass configuration respectively. The optical amplifier is not only use as the amplifier but also to support the process of generating multiwavelength fiber laser (MWFL). Three techniques demonstrated in this thesis include; multiwavelength Brillouin fiber laser (MWBFL), Sagnac loop mirror (SLM) and Fabry Perot Interferometer. The MWFL was demonstrated by various configurations to investigate the performance including its peak power flatness and tune ability. The MWBFL generated from nonlinear effect of stimulated Brillouin scattering (SBS). The Brillouin threshold power required to generate SBS in O-band is less than threshold of C-band. The MWBFL demonstrated in 2 different cavites namely linear cavity and ring cavity. Both cavities produce 4 Stokes with the linear cavity giving a iii closed spacing of 12.5 GHz while ring cavity 25 GHz. Inserting BOA in the multi pass linear configuration induce nonlinearity and hence produces 3 anti-Stokes signals. The flatness of MWBFL achieved via 2 techniques namely by in cooperate the BiDF in the cavity to provide FWM effects and by relocating the BOA. The spacing tunability for MWBFL is limited to two spacing 12.5 GHz and 25 GHz. Sagnac loop mirror were also demonstrated in linear and ring cavity, where the linear cavity provide stable and more number of channels (~16). The uniformity of MWFL via SLM was provided by the nonlinearity of BIDF. The tunability of the SLM is controlled by the length of polarization maintaining fiber (PMF). The FPI was only demonstrated in linear configuration. The spacing generated was double of SLM with the same length of PMF. The uniformity of peak power was also improved by the incorporation of BiDF. The tunability is achieved by controlling the polarization state. The spacing varied from 5.0 nm to 1.25 nm with 4 m PMF

Tunable spacing of O-band Multiwavelength Brillouin fiber laser

A tuneable spacing of O-band multiwavelength Brillouin fiber laser is demonstrated. The channel spacing is varied by employing two types of cavities. A full closed linear cavity produce multiwavelength Brillouin fiber laser with 12.5GHz meanwhile a ring cavity provide channel spacing of 25.0 GHz. By combining these two cavities and employing optical channel switch the channel spacing are varied. The comparison of Brillouin threshold between O-band and C-band demonstrated. An O-band transmission window is used instead of C-band due to its lower Brillouin threshold

Dual-Wavelength Erbium Fiber Laser in a Simple Ring Cavity

By controlling the cavity loss of the modes using a variable optical attenuator, specific intensities of distributed modes can be fed back into the erbium-doped fiber to produce signals without mode competition, thus resulting in stable lasing as a means to overcome mode competition in a homogenous gain medium. Two lasing signals were obtained with peak powers of approximately -3.475 dBm and -4.386 dBm for wavelengths of 1,540 nm and 1,548 nm, respectively, with a side mode suppression ratio of more than 43 dB

Non-membrane optical microphone based on longitudinal modes competition

We propose and demonstrate a simple and cost effective non-membrane optical microphone (OM) consisting of only a standard erbium doped fibre amplifier (EDFA) and a 25 km of conventional single mode fibre (SMF) as the sensing medium. A photo detector is used for data acquisition. The proposed setup utilizes the disturbances in the competing longitudinal modes in a low reflectivity fibre resonator whereby airborne acoustic waves impacting the surface of the fibre will modulate the intensity of the optical signal in the fibre. This modulation frequency is analyzed using the fast fourier transform (FFT) technique to extract the information embedded in the optical signal. The experiment shows that the system is capable of picking up the airborne acoustic waves and can find many potential applications

Tunable laser generation with erbium-doped microfiber knot resonator

A tunable laser is demonstrated using a microfiber knot resonator structure made by erbiumdoped fiber (EDF). The laser is made of a 2 m long EDF where 30 mm of its end section is tapered to construct a microfiber knot resonator (MKR). The combination of the EDF and MKR generates a stable single wavelength laser at 1555 nm wavelength with a signal to noise ratio (SNR) of 33.7 dB using a 63 mW of 980 nm pump power. The peak wavelength of the laser can be tuned by 340 pm as the MKR diameter reduces from 5.0 to 0.5 mm with an acceptable penalty in output power

Tunable microwave photonic frequencies generation based on stimulated Brillouin scattering operating in the L-band region

: A tunable up frequencies of microwave photonics based on stimulated Brillouin scattering (SBS) for application in radio over fiber is demonstrated. The experimental setup consists of 7.7 km dispersion compensated fiber, which acts as the nonlinear medium for generating the SBS and is pumped by a narrow linewidth (0.015 nm) tunable laser operating in L-band region. The input-modulated RF at 2 GHz is upshifted to new frequencies of 7.71, 7.68, 7.65, 7.62, 7.58, and 7.56 GHz at Brillouin pump wavelengths of 1580, 1585, 1590, 1595, 1600, and 1605 nm, respectively. This system allows certain tunability in the upshifted frequencies by using a tunable laser source. VC 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1710–1713, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.2610